A. Field of the Invention
The invention relates to roofing and specifically to roofing ventilation. The ventilated roof system and method of the Invention provides full ventilation of the underside of the roof deck, prevents blinding of ventilation intakes by attic insulation, provides a secondary barrier to water intrusion into the living space of the building, allows elimination of soffits in roof construction, and allows escape of water vapor from the interior of the building.
B. Statement of the Related Art
The portion of a building roof that is exposed to the elements is protected by a durable, weather-resistant surface, such as shingles. As used in this document, the term ‘shingle’ means tab shingles, architectural shingles, cementatious shingles, metal shingles, slate, sheet metal, tar paper, underlayment, roll roofing, ceramic tile roofing, wood shakes, synthetic versions of any of the above and any other weather proofing product that may be applied to a pitched roof.
The shingles are supported by a roof deck. As used in this document, a ‘roof deck’ means the generally planar structural covering the upper side of a building and providing support for shingles. The ‘roof deck’ usually is composed of wood in the form of plywood sheets or dimensioned lumber. The term ‘roof deck’ also may include other roofing materials previously applied to the plywood or dimensioned lumber, such as tar paper or other underlayment, ice and water shields, and shingles.
The roof deck has a pitch from the eave (lower edge) of the roof to the ridge of the roof so that water and snow will fall from the roof. As used in this document, the term ‘ridge’ means a high location on a roof, such as where the roof deck intersects another roof deck for a gable or hip roof or intersects a vertical wall for a shed roof.
To apply shingles to a roof deck, the roof deck is first covered by underlayment. The course of shingles proximal to the lower edge of the roof is then nailed to the deck over the underlayment. Each subsequent course of shingles proceeding from the lower edge to the ridge of the roof overlaps the preceding course and is nailed to the roof deck so that water running from each shingle flows onto the top of the adjacent downhill shingle. The underlayment and shingles cooperate to form a composite surface that is tight to rain water, snow melt and water vapor.
The roof deck is supported by rafters that extend from the eave to the ridge of the roof. The ends of the rafters at the eave are covered by a fascia board. As used in this document, the term ‘attic’ refers to an attic and also refers to any other air space under a roof assembly, such as the space between a ceiling or insulation and a roof deck of a structure equipped with a cathedral ceiling.
Moisture in the form of water vapor is released into the air inside a structure by the occupants of the structure, by the building plumbing systems and by the soil underneath the structure. If that water vapor is trapped under the impermeable shingle roof, the resulting condensation can damage the roof, can damage the remainder of the structure and can promote growth of mold within the attic. To avoid these effects, the space underneath the roof must be ventilated. Ventilation also serves to allow air heated by solar gain to escape from the space under the roof, reducing the cooling load on the building. During daylight hours, the sun shining on the roof warms the roof deck, causing the roof deck to be warmer than the ambient air. The warm roof deck warms the air immediately below the roof deck. During cold weather, heat within the inhabited space of the structure will leak into the attic space, which also warms the air in the attic space. The air within the attic that is warmed by the sun or by escaped building heat expands, becomes buoyant, and tends to rise. Because the roof is pitched, the warm air rises along the roof deck toward the ridge of the roof. The warm air can be released from the ridge by a ridge vent or at the gable from a gable end vent.
Warmed air escaping from the ridge vent will place the attic space at a lower air pressure than the ambient pressure outside the attic. For effective ventilation, eave vents are provided to allow make-up ambient air to enter the area under the roof. A roof equipped with eave and ridge vents acts as a large, low-pressure air pump, pumping air out through the ridge vent and in through the eave vents. The power input to the roof air pump system is heat energy generated either by sunlight shining on the roof deck or by heat leaking into the attic from the heated living space of the structure. If any portion of the roof is starved for ventilation air, then the lack of air flow through the air-starved attic space may cause the problems associated with excess moisture.
Any roof ventilation system must deal with building insulation. Insulation may be applied between joists of an attic space or may be applied between rafters supporting a roof deck. If the insulation blocks the flow of air along the underside of the roof deck, the evils of inadequate ventilation will occur. A problem location in prior art roof ventilation systems is the area of the eaves of the roof. Insulation installed proximal to the eave may block the air intakes, preventing the flow of ventilation air through the attic. Insulation applied between the rafters also may block ventilation air and may be separated from the underside of a roof deck by a baffle, frequently composed of styrofoam. Any improper installation of the baffle or of the insulation can block the flow of air, resulting in excess moisture and condensation. Ventilation air also may be blocked by anything that gets in the way of the air, including the building structure or building debris.
The present invention is not taught by the prior art.